Beryllium filament



Patented Mar. 1927.

UNITED STATES PATENT OFFICE.

ASSIGNOR '10 DU BILIER CONDENSER COR- A CORPORATION 01' DELAWARE.

IBERYLLIUI FILAKEN'I.

- Kc Drawing. Application flied November 7, 1814, Serial No, 748,464. Benewed'larch 4, 1926.

This invention relates to an improved electrical conductor or filament; especially a filament for the emission of electrons.

"An object of this invention is to provide 5 a filament preferably of the typee utilized in thermionic valves or vacuum tu s of such a character as to afford a relatively large output and high activity, with a comparatively small expenditure of power, and capable of greater durability in service.

' The nature of this invention is fully disclosed in the following description; but I, of course, may resort to chan es in details to the full extent consistent With the'broad and general meanings of the terms in which the appended claim are expressed.

' An electrode or filament according to this invention, is made of the chemical element beryllium, which belongs to the alkaline 2o earth group of chemical elements such as barium, strontium and caesium. All of these substances emit electrons freely even at low temperatures, and barium and strontium are extensively used in the form of oxides for coating the filaments of vacuum tubes, in order to afford the emission of electrons at relatively low temperatures of the filament, and with a small consum tion of electrical current assing through tlie filament.

It is own that the meltin point of beryllium is quite high, 1280 degrees C., which is higher than the melting int of other alkaline earth elements, and in other ways this element is admirably adapted to withstand conditions to which operation in a yacuum tube connected to a radio circuit, for instance, will expose it.

In accordance with my invention a beryllium filament can be made in various ways, as beryllium is quite ductile and no more oxidizable than aluminum. A piece of beryllium, therefore, can be easily drawn into wire of the required fineness, and such a mounted in a vacuum tube it wi filament needs no oxide coatingl.

P electrons in the quantity required, with rel- When roduce atively low current, to the same extent as like on their ow temperature, besides being quite inexpensive to reduce.

In practice I can utilize commercial beryllium whic' is, of course, impure, and may not contain more than 75% of beryllium, the remaining ingredients being of a different nature and imparti 0 no emissivity. Such commercial beryllium, however, is quite suitable for my purpose, and contains enough of the beryllium to make a cheap filament havin the properties above-mentioned, with a high meltlng point, suflicient ductility and durability, and requiring no oxide coating; while at the same time, having a capacity to emit electrons in large uantity with little electrical power and a ow temperature of operation.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States is A filament for emitting electrons, said filament consisting essentially of beryllium.

Si ed at New York city in the county of ew York and State of New York this 6th day of November, A. D. 1924.

ALEXANDER NYMAN. 

